A. Field of the Invention
The present invention relates to the field of network communications and, more particularly, with the configuration of network devices in a data network.
B. Description of Related Art
Cable television service providers are taking advantage of the extensive reach of the cable network infrastructure to offer high-speed data network access to users of computing equipment, such as personal computers. Channels on the cable television network may be allocated for use as data network access channels to exploit channel bandwidths of 6 MHz on a medium having a frequency range of up to 1 GHz.
Subscribers of cable service may access data network services by connecting computers to the cable network using cable modems. Subscribers may also access data networks via one or more cable modems connected on a local area network. A cable modem has a radio interface connection to a broadband coaxial cable infrastructure and a data interface connection to the computer, or to a computer network. When used to connect a computer to the cable network, the cable modem may operate internal to the computer in a card slot with a direct connection to the bus system in the computer. The cable modem may also operate external to the computer with an external connection (e.g. Ethernet, serial, etc.) to the cable modem data interface.
Data networks connected to a cable network form what are called Data Over Cable Systems. Data over cable systems use a device called a cable modem termination system as an intermediary between a number of cable modems connected over the coaxial communications medium and a data network. The data network may also include a connection to the Internet. The cable modem termination system operates along with other system components in a “head-end” of the cable network. A cable service provider uses the cable modem termination system to distribute services to the cable modems connected to it. The cable modem termination system also provides facilities that may be used to manage the resources available to the cable modems.
Cable modems may operate on a bi-directional cable system or on a uni-directional cable system. In a bi-directional cable system, the cable modems may communicate with the cable modem termination system over the coaxial medium in both directions. That is, the cable modems may transmit and receive data to and from the cable modem termination system over the coaxial medium.
In an uni-directional cable system, data is communicated over the coaxial medium in a “downstream” direction only. That is, the cable modem may only receive data from the head-end of the cable network over the coaxial medium. The cable modem may transmit data in the “upstream” direction to the head-end of the cable network using an alternative communications device; such as by a telephone connection over the public switched telephone network (PSTN). Because cable networks have been traditionally used as a broadcast medium for cable television, most data over cable systems are still unidirectional systems.
Uni-directional and bi-directional data over cable systems perform a procedure for configuring the cable modems to connect to a data network. The Dynamic Host Configuration Protocol (DHCP) is used by devices that are connected to networks, such as the Internet, to obtain configuration parameters and other information that make it possible for the devices to communicate on the Internet. The devices perform the DHCP protocol as clients that query a DHCP server during the initialization procedure performed by the device at boot up. Once the DHCP server responds with the appropriate parameters, the devices may begin to communicate by sending and receiving packets on the Internet. The DHCP may be used by client computers and by cable modems that are connected to a data over cable system.
The parameters that a device may obtain using the DHCP include an Internet Protocol address (IP address), a list of domain name servers, a domain name, the lease time of the IP address, a default gateway for the device, a trivial file transfer protocol (TFTP) server address and TFTP file name. The DHCP has been adopted by the industry as a standard protocol that is documented in RFC 2131. The RFC 2131 describes the many parameters that may be obtained from the DHCP server. The RFC 2131 also describes instructions for communicating with the DHCP server. In a data over cable system, client computers and cable modems each use configuration parameters from a DHCP server before communicating on a data network. The cable modems obtain parameters during the initialization and registration process. The client computers may also obtain configuration parameters during system initialization.
The client computer uses the cable modem to access the data network, and thus, to access the DHCP server. However, until the cable modem is properly initialized, registered and fully connected, it cannot perform communications functions for the client computer or computers to which it is connected. This may cause problems for client computers in a variety of scenarios. For example, a computer may attempt to use a bi-directional cable modem to issue DHCP messages before the RF cable has been connected to the cable modem. In addition, if the cable modem and the computer are on the same power strip or if an internal cable modem is used and powered by the computer's bus system, the two always power-up simultaneously. If it takes more time for the cable modem to power-up and to become initialized and registered than for the computers to perform DHCP messages, the DHCP messages will not be communicated. In such situations, the connection may become permanently shut down.
Moreover, any client computer that obtains configuration parameters from a DHCP server connected to a data network to which it accesses via a communications device, such as a modem, or a gateway, may experience the same difficulty. If the communications device takes more time to initialize than it takes the client computer to begin requesting configuration parameters, the client computer may not be able to access configuration parameters from the DHCP server. Because a failure to retrieve configuration parameters is typically treated as an error, the client computer may require a restart to begin another request for configuration parameters. Where the communications device is connected to the client computer system bus, the communications device is reset whenever the client computer is reset. The client computer may never obtain configuration parameters in such a scenario permanently shutting down its connection to the data network.
It would be desirable to ensure DHCP operation on a client computer without the risk of permanently losing the connection through the communications device if the communications device is also not yet ready or able to perform DHCP messages from the client to the server.
It would be desirable to ensure DHCP operation on a client computer without the risk of losing the connection through the cable modem permanently if the cable modem is not yet ready or able to perform DHCP messages from the client to the server.